Senior Investigating Officer, Detective Chief Inspector Victoria Short, of South Yorkshire Police, said: “At this time, we are treating Caroline’s death as unexplained.

“There have been a number of developments throughout the late evening and overnight as part of this complex investigation.

“A post-mortem examination was completed however the cause of death was not established and the results were recorded as inconclusive. Further tests have now been requested.

“Officers have trawled through hours of CCTV footage to trace Caroline’s last steps to begin to understand what happened that night.

“CCTV tells us that Caroline left the Corporation nightclub on Milton Street at around 2.40am on Sunday.

“A minute later, she is seen with a man outside the Devonshire Cat pub. At 3.35am, CCTV shows them parting company on Napier Street in Sharrow.

“Approximately ten minutes later, Caroline is seen alone on Summerfield Street, walking in the direction of the river. This is the last we see of her.

“We have carried out extensive enquiries in a bid to identify and locate the man in the earlier CCTV footage. As a result, we arrested a 31-year-old on suspicion of rape. He remains in custody.

“The investigation is ongoing and we continue to review CCTV footage from the information received from the public.

“If you saw Caroline that night, or have any information, I urge you to come forward. Any information, no matter how small, could be vital to piece together her final steps and to provide answers for her family.”